At the end of what has been a long, strange, 10–year trip, Navistar is the only North American engine manufacturer which will offer fleets an “EGR only” approach in 2010. All other OEMs – including Cummins, Detroit Diesel, Isuzu, Mack, Mercedes-Benz and Volvo will use SCR systems. SCR is an additional emissions control system that will be mounted on heavy duty trucks next year to reduce emissions in diesel exhaust after the engine’s EGR system has done its work to the soot and NOx produced in the engine.

As a vocational truck owner, these changes will dramatically impact the way you spec and maintain your vehicles. Acquisition costs will increase regardless of which technology you opt to go with. But other variables will come into play as well, for trucks ranging from Class 3 up to Class 8: Some trucks will see an increase in gross vehicle weight. SCR technology will require the purchase of a new, mandatory diesel exhaust fluid (DEF).

And careful consideration will have to be given to the placement of these components on trucks engaged in severe, off-highway applications. Still, both proponents of SCR and EGR technology insist their emissions solutions will not only work, but excel in tough, construction applications..

Even casual trucking industry observers have surely noted the war of words that has erupted between EGR and SCR proponents. Navistar has ridiculed SCR technology as “stop-gap” in nature, adding additional weight to truck chassis, adding to driver responsibilities by requiring them to fill an additional DEF tank and charging that DEF itself is a toxic, hazardous substance.

In response, SCR engine manufacturers have noted that DEF has been used successfully in industrial applications and on European trucks for years without issue. In addition, SCR proponents say, their new technology will boost Class 8 fuel economy and argue it is simply impossible to meet EPA ’10 regulations using EGR alone and insist Navistar would be unable to do so without cashing in EPA credits.

Navistar actually filed a lawsuit in Federal court arguing that SCR on-board diagnostic systems that de-rate a truck’s power and performance as an inducement to refill an empty DEF tank allow the trucks to run in violation of the EPA ’10 and should therefore be ruled in violation of those regulations.

“SCR isn’t voodoo,” says Dave McKenna, director of powertrain sales and marketing for Mack Trucks. “SCR technology has been around since 1957 in commercial and industrial applications. It’s a simple means of removing NOx from our atmosphere.”

As exhaust gases leave the engine, but before they exit a truck’s exhaust pipe, they flow through a catalytic converter where they are sprayed with a solution of 67.5 percent deionized water and 32.5 percent urea. When the super-hot NOx combines with the urea in this solution (DEF), it chemically converts into environmentally harmless water and nitrogen.

“SCR isn’t voodoo. SCR technology has been around since 1957 in commercial and industrial applications.”

Measured at the exhaust stack, 2010 diesel engines will be allowed to emit only .02 percent of a gram of NOx into the atmosphere. Thanks to Environmental Protection Agency (EPA) credits it accumulated for its 2004 engines, which performed in excess of then-existing regulations, Navistar is technically allowed to sell engines that emit .05 percent of NOx after January 1, 2010. Both the US and the California Air Resources Board (CARB) recognize ‘Averaging Banking and Trading’ (AB&T) programs for manufacturers to certify heavy duty diesel engines, Tim Schick, director business and product strategy for Navistar Engine Group explains. Under the program, manufacturers may bank or consume emissions “credits” for engines that are certified either below or above the current standard. For example, an engine subject to the current 2007 standards may be certified to ’bank’ credits if the engine’s emissions are certified below the prescribed 1.2 gram NOx limit. These banked credits can then be “traded” to “average out” higher emitting engines in the same year or future years. One key stipulation: as the credits are used they are discounted by 20 percent.

In this way the program benefits the environment with cleaner engines earlier to create and bank credits and cleaner engines forever as the credits are used because of the discount factor. The program provides flexibility for engine manufacturers and several manufacturers including Navistar have participated either in the past or currently.

Of all the engine manufacturers, Navistar and Cummins benefited the most from the EPA’s credits program. Not only did they develop engines that performed better than required under various EPA regulatory phases, but thanks to their respective relationships with the Ford SuperDuty and Dodge Ram light-duty truck lines, the companies were able to sell engines in higher volumes than companies that catered to heavy-duty truck markets alone. Neither company will state publically how many credits it has amassed, or how long they expect them to last. What is clear is that using the credits gives Navistar additional time to perfect its EGR-only engine solution or take advantage of developing emissions technologies such as on-board urea-generation systems.

“As of right now we are an EGR-only engine manufacturer. And there is no indication we will manufacture or offer independent engine brands with SCR on our trucks.”

— Tim Shick, director business and product strategy for Navistar Engine Group

Credits, or no, Shick is firm in saying Navistar expects to meet the .02 gram requirement by 2012 using only EGR. “The difference between today’s engine and the .05 version we’ll release next year is higher fuel pressures and a higher EGR rate, “he explains. “And the difference between .05 engines and our .02 engines will be even higher fuel pressures and EGR rates.”

Not surprisingly, Navistar’s competitors dispute these claims. “The 2010 EPA regulations represent an 83 percent reduction in NOx from the (current) 2007 standards,” notes David Siler, director of marketing for Detroit Diesel. “Those goals cannot be attained without SCR. No technology in the world can get you there alone. So SCR is here and will be here for a long time to come.”

Navistar, however, is sticking to its guns. “As of right now we are an EGR-only engine manufacturer,” Shick stresses. “And there is no indication we will manufacture or offer independent engine brands with SCR on our trucks. We’re looking really good with where we’re going with EGR. People say, ‘Well why don’t you just meet 2010 now?’ We could. But, meeting the .02 isn’t the challenge.

If you put enough exhaust gas back into the engine, you’re going to get to .02, eventually. The challenge is recalibrating iteration after iteration after iteration to make sure you get the very best fuel economy and performance possible. And that’s what takes time to do.”

Shick says Navistar is going with EGR-only because of the simplicity of the design, noting that SCR will add from between 300 to 600 pounds of additional components to a heavy-duty diesel truck, depending on its size.

Additionally, drivers will not have worry about filling an additional tank with diesel exhaust fluid, nor will they have to worry about the engine derating if the urea tank runs dry.

But SCR has advantages, too, proponents say. “For the most part fuel economy has taken a hit with each level of EGR that has been implemented,” says Rich Moskowitz, public affairs counsel for the American Trucking Associations. “According to our members, most fleets saw on average an 8 percent hit since EGR’s lower combustion temperatures reduce engine efficiency.”

Because of greater combustion efficiency, Detroit Diesel’s Siler says trucks equipped with SCR will see significant improvements in fuel economy. “Our 2010 DD15 engine will get between 3 and 5 percent fuel economy than our current engine and we think those numbers will only improve in the long run,” he says. “Most fleets would switch engines over a 2 percent increase in fuel economy. So even after factoring in the new cost of buying diesel exhaust fluid, we believe — that for the first time – that our emissions technology will actually deliver a positive economic impact for end users while delivering clean air to our environment.”

Given all the passion and controversy surrounding DEF, the fluid itself is largely unremarkable. It’s colorless and odorless. It is not classified as a hazardous or toxic material by the EPA. “Some of the claims that were made were about DEF over the past couple of years are patently untrue,” says Ed Saxman, product manager, drivertrains, Volvo Trucks. “DEF is not explosive, it’s not flammable, it’s not an aggressive substance. Put it on your hands and they are no less irritated than if you get diesel fuel on them. You want to go wash your hands, of course, but it’s not any worse than that. It’s mostly water. It has a residue to it when it dries, but that easily washes off.”

Siler says it’s important to remember that DEF usage rates are only 2 to 3 percent of a truck’s fuel consumption. “Daimler tanks will be offered next year with 6, 13 and 23 gallon DEF tanks. (We suspect the 13-gallon option will be the most popular.) For some perspective, a 23 gallon DEF tank gives you a range of 6,000 miles before a refill is necessary. A 13 gallon tank will have a range of 3,900 miles before a refill is needed.”

If a DEF tank does run dry, the driver will have powerful incentives to pull over and fill it back up. In Daimler trucks, a series of color-coded dash lights green, yellow and red – in addition to a DEF gauge – will keep a driver informed of the tank level. When the DEF tank runs dry, or if sensors detect high emissions due to improper fluids in the tank (water, for example), the engine will derate to 35 mph – enough to get to a refill point for the DEF tank. Eventually, the engine will derate to only 5mph in extreme cases. But given DEF’s long legs, Siler thinks it is highly unlikely drivers will be unable to find DEF and keep their tanks full.

As for DEF’s freezing at 12 degrees, that’s simply chemistry. But all SCR manufacturers have placed immersion heaters in their DEF tanks. And as Mack’s McKenna explains, DEF thaws rapidly and is not adversely affected by freezing. “SCR trucks will start and run with frozen DEF in the tanks,” he stresses. “We have done extensive cold-weather testing and found no operational issues related to frozen DEF.”

Gregg Stumbaugh corporate equipment director, with California-based Biachi Brothers is worried about the additional cost of SCR technology, which some analysts predict could be as high as $8,000 per new truck and the additional weight SCR adds to each chassis. “We also don’t know enough about the additional costs for maintenance and repair of SCR systems over the life of the truck,” he notes. “And we don’t know how reliable the SCR system as a unit will be over the life of the truck. The bottom line is that our company does not want to be a “guinea pig” for the SCR system. We are in the process of running a demo International truck with the Maxforce engine with the enhanced EGR system and see the International as a possible option.”

Although Shick believes EGR will work well in all trucking applications, he feels there are specific applications where it will prove to be the preferred emissions solution. “Since the big advantage of EGR is it adds no weight and bulk from additional apparatus and requires no technician/driver involvement, we think its biggest impact would probably come in complex vocational body applications like aerial lift trucks, municipal vehicles/snowplows, digger derricks, and refuse packers that will be challenged by additional weight/bulk of SCR apparatus,” he says.

It’s an argument Detroit Diesel’s Siler isn’t buying. “With the Detroit Diesel BlueTec emissions technology we know that our customers will benefit from not only better fuel economy but also a cleaner running system,” he counters. “Plus, we aren’t ready to concede the question regarding complexity and packaging. With Damiler’s BlueTec 1-Box system we have been able to integrate the aftertreatment and chassis into a surprisingly compact and simple design. In 2010, we expect at least 80 percent of all 2010 compliant trucks to be SCR.Eventually, we believe that share will increase even more as the full benefits of SCR are proven.”

“Remember,” says Saxman, “SCR is not new technology. It’s been used for five to seven years around the world in heavy trucks and other applications for even longer. We’ve built well over 150,000 trucks in our group of companies with SCR and have over 2 million test miles on SCR trucks in the United States alone. The emissions technology we introduced in both 2002 and 2007 was all new, by comparison. We’re going into to 2010 with far more testing and experience behind SCR than we ever had on our previous emissions systems.”v

Diesel Exhaust Fluid

Its basic stats are pretty straightforward: Diesel exhaust fluid (DEF) weighs 9.2 pounds per gallon. It starts to turn to a gel at 25 degrees Fahrenheit and freezes at 12 degrees. And it is true that onboard sensors will derate an SCR-equipped truck if DEF is not being injected into its exhaust stream – whether because of a frozen solution or a dry DEF tank.

There are some warm-climate DEF concerns as well. Despite rumors that DEF breaks down at 86 degrees, Fahrenheit, David Siler at Detroit Diesel says testing has shown it has a shelf life of 44 months when kept at a constant 74 degrees and can last as long as 7 months at 95 degrees.

Still, the lack of a DEF infrastructure in the United States was an initial reason the EPA opposed SCR technology when it was first suggested as path for meeting EPA ’10. According to Cliff Dean with the EPA’s Office of Transportation and Air Quality, the agency is now convinced DEF will be readily available in January and is, in fact, the best way available now to meet emissions regulations when they come in effect.

Brendan Foster, president of DEF pump distributor, Benecor, agrees. “I believe DEF will be easily available, but more common as a packaged product initially. Due to the economic conditions that the country is facing, the market has taken a definitely more conservative approach to how they roll out larger quantities.”

The engine maker changed course and announced in August 2008 that it would use selective catalytic reduction (SCR) with heavy-duty engines. It says the U.S. Environmental Protection Agency has no concerns regarding the use of its copper zeolite-based catalyst, which the engine maker says provides a much higher NOx conversion efficiency than iron zeolite catalysts. Cummins also says it is on track to exceed its field test mileage target for both its heavy-duty and midrange engine lines. At production launch in January 2010, Cummins heavy-duty field testing will top 3 million miles, and midrange field testing will approach 2 million miles. The company reports positive feedback on performance and fuel economy from field test customers.

Detroit Diesel says it designed the DD13, DD15 and DD16 engines with 2010 emissions regulations and SCR aftertreatment in mind, so the engines themselves will see virtually no changes from the current design. The company says its 1-Box BlueTec SCR design integrating the diesel particulate filter (DPF) offers compact packaging and enhanced exhaust flow.

Mack says its engines do not change for 2010. The company introduced the first member of its Mack MP engine series – the 11-liter MP7 – in late 2005 in an EPA ’04 configuration. Now, for EPA ’07, Mack offers the MP7, MP8 (13-liter) and recently-introduced MP10 (16-liter). All were designed from the beginning with the EPA’10 regulations in mind.

Navistar says no changes will be made to its exhaust gas recirculation (EGR) MaxxForce 11 and 13 big bore engines for 2010, and there will not be an SCR aftertreatment system. Navistar says its 2010 engine models have been in commercial service since January 2007 and have logged hundreds of millions of real-world miles. Navistar plans to introduce a 15-liter MaxxForce 15 in early 2011 and will bridge the gap with a combination of 2009 engines carried over into 2010 and a transitional 15-liter engine that it isn’t yet discussing publicly. Navistar also believes that many customers will choose to move from 15-liter to 13-liter engines due to weight and fuel economy.

The parent company for both Kenworth and Peterbilt trucks has not released the exact number of test trucks in its test program, nor the miles that program has accumulated to date. A company spokesman says Paccar is actively testing the 2010 engines – through field tests with customers, with trucks running on its test tracks and road tests conducted by company personnel, and in test labs to identify issues and validate components and installations – and notes the company is planning for engine availability in January 2010.

There will be no changes to Volvo’s family of diesel engines in 2010 beyond the addition of SCR aftertreatment systems to meet EPA ’10 emissions requirements. Volvo has more than 150,000 SCR trucks on the road in Europe and has logged more than 2 million test miles on its 2010 engines in the United States alone. The manufacturer also emphasizes that its 2010 solution will eliminate active regeneration of DPFs during normal highway operations.

How SCR Works

*The charge-air cooler cools air from the turbo back down to outside temperature, reducing NOx, particulate and engine stresses.

**The hydro-carbon doser injects fuel to heat the exhaust during active regeneration of the DPF.

*The exhaust reacts with the DEF in a decomposition reactor, turning the urea into ammonia.

*The ammonia then reacts with NOx in the selective catalytic reduction catalyst. NOx is natural nitrogen combined with oxygen because of high cylinder temperatures. SCR turns 85 percent of engine-out NOx to nitrogen and water.